To solve the problem it is necessary to apply the concepts related to Force of Friction and Tension between the two bodies.
In this way,
The total mass of the cars would be,


Therefore the friction force at 29Km / h would be,




In this way the tension exerts between first car and locomotive is,



Therefore the tension in the coupling between the car and the locomotive is 
Option D) A drop of mercury is both a pure substance and and element.
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<h2>Answer: free electrons</h2>
<u>Plasma</u> is known as the 4th state of matter and is itself ionized gas. In this sense, ionization consists of the production of ions, which are <u>electrically charged atoms or molecules due to</u><u> the excess or lack of electrons</u><u> with respect to a neutral atom or molecule.
</u>
That is why in this process there are always<u> free electrons</u>. Therefore in heating gas to create plasma can yield free electrons, and the correct option is D.
Answer:
We know that for a pendulum of length L, the period (time for a complete swing) is defined as:
T = 2*pi*√(L/g)
where:
pi = 3.14
L = length of the pendulum
g = gravitational acceleration = 9.8 m/s^2
Now, we can think on the swing as a pendulum, where the child is the mass of the pendulum.
Then the period is independent of:
The mass of the child
The initial angle
Where the restriction of not swing to high is because this model works for small angles, and when the swing is to high the problem becomes more complex.
Answer:
16.2 days
Explanation:
Find the number of halflives:
1/2 * 1/2 = 1/4 so <u>two</u> halflives have passed
2 * 8.1 days = 16.2 days